Pseudoceros vishnui, Dixit, Sudhanshu, Raghunathan, C. & Chandra, Kailash, 2017

Dixit, Sudhanshu, Raghunathan, C. & Chandra, Kailash, 2017, Two new Pseudoceros (Polycladida: Pseudocerotidae) and a Prostheceraeus (Polycladida: Euryleptidae) from Andaman and Nicobar Islands, India, Zootaxa 4269 (4), pp. 495-512 : 501-503

Pseudoceros vishnui sp. nov.

Figures 6–8 ; Table. 1

Type material: Holotype: One specimen (20 x 15 mm) as serial sections of reproductive structures (7 Slides), remainder of animal in 70% ethanol. Collected 19.03.2015, subtidally from 10 m depth, Pongibalu (Lat: 11°30.573’N, Long: 92°39.123’E), South Andaman, India (ZSI/ANRC-16841).

Paratypes: One specimen (15 x 10 mm) as serial sections of reproductive structures (5 Slides), remainder of animal in 70% ethanol. Same as holotype (ZSI/ANRC-16842).

One specimen (11 x 8 mm) in 70% EtOh. Collected 0 8.09.2015, subtidally from 15 m depth, Pongibalu (Lat: 11°30.573’N, Long: 92°39.123’E), South Andaman, India (ZSI/ANRC-16843).

One specimen (11 x 8 mm) in 70% EtOh. Collected 15.12.2016, subtidally from 9 m depth, Rutland Island (Lat: 11°30.119’N, Long: 92°37.112’E), South Andaman, India (ZSI/ANRC-16844).

Distribution. Pongibalu, South Andaman, India. Additional photographic record from Burma ( Newman & Cannon, 2005).

Diagnosis. Body colour cream, solid purple to violet spots all over body. Margin made up of non-continuous dark blue spots of various sizes.

Etymology. This species is named after Vishnu Kumar Dixit, father of the first author, in acknowledgment of his support throughout his research on marine flatworms.

Synonyms. It is likely that it corresponds to Pseudoceros sp. 38, Newman & Cannon (2005), CD-ROM and to Pseudoceros sp., Kuiter & Debelius (2009), see taxonomic remarks below.

Description. Live. Body oval and smooth, margin without any ruffles. Many purple to violet coloured spots, of variable sizes, more or less circular are present all over the body ( Fig. 6A , B). Blue pseudotentacles, small, formed by simple folds of the anterior margin with scattered eyespots on each pseudotentacle on either side. Cerebral eyespot cluster with 40–43 eyes ( Fig. 6 C). Ventral side cream in colour. Margin made up of small blue coloured discontinuous spots of various sizes.

Preserved. Holotype 15 mm long and 12 mm wide at central portion. Translucent due to loss of colour on fixation but some faint purple spots visible in paratype specimen. Dorsal epidermis very rough and uneven with thickens 45 to 55 µm and is twice the thickness of ventral epidermis which is 18–22 µm and smooth. Nucleus present at the base while rhabdites near dorsal surface. A distinct basement membrane clearly separates epithelium from underlying muscles. Distance between pharyngeal mouth and sucker is 4.53 mm. Male and female gonopores 1.03 mm apart. Pharynx small and ruffled with 7 folds . Male pore 1.93 mm from pharyngeal mouth and is situated between last pair of pharyngeal folds. Sucker 1.3 mm from female pore.

Reproductive characters. Measurements refer to length in a 15 mm long worm, the holotype. Seminal vesicle ( Fig. 7 A) elongate and oval (490 x 421 µm), heavily muscularized, parallel to longitudinal body axis. Prostatic vesicle ( Fig. 7 A) located anterior to seminal vesicle and just above male atrium. It is slightly tapering in shape downwards (180 x 168 µm) with thickness of inner wall varying from 30 to 50 µm. Male atrium deep with many folds and stylet 197 µm long. Female atrium 188 µm long while vagina is 384 µm long tube curved towards posterior end. Well defined cement pouches with numerous cement glands present ( Fig. 7 B & 8).

Taxonomic remarks. The presence of this species is recorded on many occasions from Andaman Islands ( Sreeraj & Raghunathan 2013; Sreeraj et al. 2015); however, no attempt had been made in the past to make a formal description. To date, only 4 species under the genus Pseudoceros are described from India: Pseudoceros gamblei Laidlaw, 1902 ; P. tigrinus Laidlaw, 1902 ; P. galatheensis Dixit et al. 2017 and P. nigropunctatus Dixit et al. 2017 . The general spotted pattern of newly described species P. vishnui sp. nov. resembles with P. nigropunctatus described from same geographical area but the difference in appearance and colour of the spots on dorsal surface and background colour distinguish them from one another. In addition, P. laingensis Newman & Cannon, 1998 described from Papua New Guinea is the most resembled species to P. vishnui sp. nov. in terms of margins, background colour and spots. Both species have purple spots on dorsum but the spots in P. laingensis are smaller and more in number in comparison to P. vishnui sp. nov. with bigger and few spots. Border of P. laingensis is made up of numerous purple spots (same colour as that of spots on dorsum) of different sizes ( Bolanos et al. 2016) while the border of P. vishnui sp. nov. is characterised by numerous spots of blue colour and never of same colour as of spots on dorsum. Bolanos et al (2016) mentioned that the purple dots on the dorsal surface of P. laingensis were numerous in some individuals but scarce in others while the frequency of spots in P. vishnui sp. nov. remained almost similar in all the studied individuals. There are few more species under the genus Pseudoceros with presence of spots on their body namely Pseudoceros nipponicus Kato, 1944 ; P. lindae Newman & Cannon, 1994 and P. scintillatus Newman & Cannon, 1994 . P. nipponicus have black spots on the dorsum and a russet brown sub marginal band with a black rim while P. lindae is characterised by golden yellow spots on dorsum. In P. scintillatus the spots are very big, differently coloured, clearly outlined and touching the margin. Newman & Cannon, 2005 reported this undescribed species as Pseudoceros sp. 38 from Burma and mentioned colour of spots as red and margins to be made up of purple spots. Kuiter & Debelius (2009) also reported this species as Pseudoceros sp. from Andaman Sea based on photographic record.

But the overall appearance and pattern of the species agrees to the newly described species and existence of both in same geographical area led us to assume that both can be same species. Table. 1 is provided with detailed comparisons between newly described species and similarly coloured species.

TABLE. 1. Comparison of Pseudoceros vishnui sp. nov. characters with similarly coloured and patterned species.

Figures

FIGURE 6. A. Pseudoceros vishnui sp. nov. in situ from Pongibalu; B. Pseudoceros vishnui sp. nov. ex situ; C. dorsal surface showing cerebral and tentacular eyes; D. detail of ventral surface. ce: cerebral eyes; fp: female gonopore; mp: male gonopore; p: pharynx; pm: pharyngeal mouth; su: sucker; vd: vas defrenses; te: tentacular eyes.

FIGURE 7. Pseudoceros vishnui sp. nov. A: Male reproductive system; B: Female reproductive system; C: Male atrium with stylet. cg: cement glands; cp: cement pouch; fp: female gonopore; ma: male atrium; mp: male gonopore; pv: prostatic vesicle; sv: seminal vesicle; st: stylet; va: vagina. Scale bar: 200 µm.

FIGURE 8. Pseudoceros vishnui sp. nov. diagrammatic reconstruction of male and female reproductive structures. bm: basement membrane; cg: cement glands; cm: circular muscles; cp: cement pouch; ej: ejaculatory duct; ep: epidermis; fa: female atrium; fp: female gonopore; ma: male atrium; mp: male gonopore; pd: prostatic duct; pp: penis papilla; pv: prostatic vesicle; st: stylet; sv: seminal vesicle; va: vagina.